One of the most important unifying principles of Chemistry

Patterns that develop in the elements

A table showing the elements and related information about them

Each box in the periodic table represents one element▪ It contains▪Atomic Number▪Symbol▪Average Atomic Mass

Arranged in columns called groups or families , they are organized by the number of outer energy level/ valence electrons.

18 vertical columns divided into 8-9 Groups or Families

The number of valence electrons or the reactivity level determine which group an element belongs to (In most cases the singles digit in each

group number indicates the number of valence electrons)

A horizontal row of elements in The Periodic Table. In most families, the reactivity of the

elements in the same family increases as the period increases or moves down the chart.

The smallest part of a compound, or element.

A molecule must contain two or more atoms from the Periodic Table of Elements. ▪CO2 = Carbon Dioxide▪CO = Carbon Monoxide▪Au2 = Gold

The atoms on the periodic table are called elements.

There are more than 110 known elements. ▪No element with an atomic number

greater than 92 is found naturally in measurable quantities on earth

Element can also refer to a pure molecule.

That is when a molecule has only 1 element in its composition▪O2 = Oxygen

▪Au2 = Gold

When two or more different elements combine (bond) they form a compound

Examples

▪H2O = Water

▪C6H12O6 = Glucose

▪CO2 = Carbon Dioxide

Two classifications of compounds▪Organic▪ Inorganic

A compound that contains a combination of Hydrogen (H), Carbon (C) and Oxygen (O)and derived from a living thing

Example▪ Glucose C6H12O6

A compound that does not contain Carbon.

If it does the carbon has not come from a previously living thing

Examples▪ Carbon Monoxide (CO)▪ Carbon Dioxide (CO2)

▪ Carbonates (CaCO)

The largest section located on the left side of the “stair-step line” of periodic table.

These elements are ▪Shiny▪Malleable▪Ductile▪Conductive▪High melting point (temperature)

Located to the right of the “stair-step line” on the table.

These elements are:▪Non-conductive▪No luster or not shiny, but dull

Found along the stair-step line between the metals and nonmetals.

A lot like metals but not exactly

Metalloids▪Have qualities of metals and

nonmetals▪Brittle , non-ductile and non-

malleable

Hydrogen & Helium Hydrogen▪Classified as part of Group 1 only

because it has only 1 valence electron.▪However it has its own unique set of

properties that set it apart from the other members of the group

Helium▪Classified as part of Group 8 mainly

because it has no reactivity like all of the elements in group 8. ▪Helium has only 2 valence electrons

rather that the 8 all the other members of this group do.

Dimitri MendaleevThe “Father of the Periodic Table”,

He collected all the information available in the nineteenth century about the elements

Arranged the elements by increasing atomic mass and found a repeating pattern in the physical and chemical properties

Eventually the table was rearranged by atomic number as it was more accurate that way